The present invention relates to a method of manufacturing a semiconductor device in such manner that a semiconductor wafer on which a plurality of semiconductor elements are formed is divided into individual pieces of the semiconductor elements, the thickness of the semiconductor device is not more than 100 μm. The present invention also relates to a plasma processing apparatus and a plasma processing method suitably used for the manufacturing method.
A semiconductor device mounted on a circuit board of electronic equipment is conventionally manufactured in such a manner that pins of a lead frame and metallic bumps are connected to semiconductor elements, on which a circuit pattern is formed in the state of a wafer, and the semiconductor elements are subjected to a packaging process so that they can be sealed with resin. Since the size of electronic equipment has been recently reduced, the size of the semiconductor device has been also decreased. Especially, they have been actively making investigation into the reduction of the thickness of a semiconductor element, and the semiconductor wafers, the thickness of which is not more than 100 μm, have been used.
The mechanical strength of the semiconductor element, the thickness of which is reduced, is so low that the semiconductor element is liable to break in the process of cutting in the dicing step in which the semiconductor element in the state of a wafer is cut into individual pieces, and the yield of machining is inevitably lowered. Concerning the method of cutting the semiconductor element, the thickness of which is reduced, instead of the mechanical cutting method, a plasma dicing method is proposed in which the semiconductor wafer is cut when cutting grooves are formed by the etching action of plasma. Concerning this method, for example, refer to Japanese Patent Publication 2002-93752.
This method is executed as follows. First, a face opposite to the circuit forming face is machined so as to reduce the thickness of a semiconductor wafer. When the thus machined face of the semiconductor wafer is subjected to plasma processing, stress relief is carried out in which a micro-crack layer generated on the machined face is removed. After that, a region on the semiconductor wafer except for the cutting lines is coated with resist, that is, a mask of a resist film is formed. Then, plasma processing is carried again from the mask forming face side. Due to the plasma processing, silicon in the portions of the cutting lines is removed by plasma etching, and the semiconductor wafer is divided into individual pieces of the semiconductor elements. After that, the mask is removed. In this way, the individual semiconductor device is completed.
However, in the process of cutting a semiconductor wafer of the prior art described above, the steps of stress relief, mask formation and plasma dicing are successively executed. Therefore, it is necessary to use an exclusive processing device for each step. That is, after plasma processing has been completed for stress relief, the semiconductor wafer must be picked up from the plasma processing apparatus. After the mask has been formed, the semiconductor wafer must be conveyed into the plasma processing apparatus again. Therefore, the following problems may be encountered. The manufacturing process becomes complicated, which increases the equipment cost of the production line and decreases the production efficiency. Further, when the very thin semiconductor wafer, the thickness of which is reduced by machining, is conveyed and handled between the processes, the semiconductor wafer is liable to be damaged, which inevitably decreases the manufacturing yield.